USB bandwidth monitor

Abstract

An apparatus and method for intercepting messages between the bus controller and a device attempting to connect over the bus. Based on the intercepted message, the existing device using bandwidth can determine whether it can relinquish some of its bandwidth allocation while maintaining sufficient transmission quality. Thus, the already connected devices will make the determination if they can relinquish bandwidth, to allow a new device to connect.

What is claimed is:  
     
       1. A method for varying the allocated bandwidth of a first device on a shared bus, comprising: 
       receiving notification of a request for a bandwidth allocation by a second device on said shared bus;  
       determining if said shared bus has sufficient unused bandwidth to accommodate said request;  
       if there is insufficient unused bandwidth to accommodate said request, then determining if said first device can reduce its bandwidth allocation while still maintaining transmission quality above a predefined minimum level; and  
       if said first device can reduce its bandwidth allocation while still maintaining said transmission quality above said predefined minimum level, then reducing the allocated bandwidth of said first device.  
     
     
       2. The method of  claim 1  wherein said first device is a streaming device. 
     
     
       3. The method of  claim 1  further comprising: 
       monitoring only devices of specified classes of devices for requests for bandwidth allocation.  
     
     
       4. The method of  claim 1  further comprising: 
       responding to requests for bandwidth allocation with a bus controller response; and  
       intercepting said bus controller response with a bandwidth monitor, and sending a message to said first device so that said first device can perform said step of determining if said first device can reduce its bandwidth allocation.  
     
     
       5. The method of  claim 1  wherein said steps are performed by a filter driver. 
     
     
       6. The method of  claim 1  wherein said shared bus is a universal serial bus. 
     
     
       7. The method of  claim 6  wherein said bandwidth is isochronous bandwidth. 
     
     
       8. A method for varying the allocated bandwidth of a first streaming device on a shared bus, comprising: 
       monitoring only devices of specified classes of devices for requests for isochronous bandwidth allocation;  
       receiving notification of a request for a bandwidth allocation by a second device on said bus;  
       determining if said shared bus has sufficient unused bandwidth to accommodate said request;  
       if there is insufficient unused bandwidth to accommodate said request, then determining if said first device can reduce its bandwidth allocation while still maintaining transmission quality above a predefined minimum level; and  
       if said first device can reduce its bandwidth allocation while still maintaining said transmission quality above said predefined minimum level, then reducing the allocated bandwidth of said first device.  
     
     
       9. A computer program product comprising a computer usable medium having computer readable code embodied therein for varying the allocated bandwidth of a first device on a shared bus, the computer program product comprising: 
       computer readable code embodied on said medium for receiving notification of a request for a bandwidth allocation by a second device on said shared bus;  
       computer readable code embodied on said medium determining if said shared bus has sufficient unused bandwidth to accommodate said request;  
       computer readable code embodied on said medium for, if there is insufficient unused bandwidth to accommodate said request, then determining if said first device can reduce its bandwidth allocation while still maintaining transmission quality above a predefined minimum level; and  
       computer readable code embodied on said medium for, if said first device can reduce its bandwidth allocation while still maintaining said transmission quality above said predefined minimum level, then reducing the allocated bandwidth of said first device.  
     
     
       10. The computer program product of  claim 9  further comprising: 
       computer readable code embodied on said medium for monitoring only devices of specified classes of devices for requests for bandwidth allocation.  
     
     
       11. The computer program product of  claim 9  further comprising: 
       computer readable code embodied on said medium for responding to requests for bandwidth allocation with a bus controller response; and  
       computer readable code embodied on said medium for intercepting said bus controller response with a bandwidth monitor, and sending a message to said first device so that said first device can perform said step of determining if said first device can reduce its bandwidth allocation.  
     
     
       12. The method of  claim 9  wherein said bandwidth is isochronous bandwidth on a universal serial bus. 
     
     
       13. The method of  claim 9  wherein said code comprises a filter driver. 
     
     
       14. An apparatus for varying the allocated bandwidth of a first device on a shared bus, comprising: 
       means for receiving notification of a request for a bandwidth allocation by a second device on said shared bus;  
       means for determining if said shared bus has sufficient unused bandwidth to accommodate said request;  
       means for, if there is insufficient unused bandwidth to accommodate said request, then determining if said first device can reduce its bandwidth allocation while still maintaining transmission quality above a predefined minimum level; and  
       means for, if said first device can reduce its bandwidth allocation while still maintaining said transmission quality above said predefined minimum level, then reducing the allocated bandwidth of said first device.